Figure 1.
The DSBR model in meiosis. Shown are the duplex DNA strands of two non-sister chromatids from a pair of homologous chromosomes (Homolog 1 is red; Homolog 2 is blue). Meiotic DSBs are repaired following 5′-end resection and the formation of an SEI intermediate. Elongation of the invading strand extends the D-loop until SEC initiates a second round of DNA synthesis. Ligation of the free ends creates a joint molecule containing dHJs. Resolution of the dHJs in an opposite sense (e.g., black carets shown here) leads to the formation of a CO, whereas cleavage in the same sense (e.g., cleavage of the crossed strands) results in an NCO. Resolution consists of two steps: symmetric cleavage to produce duplex DNA with nicks (open carets) and ligation of the nicks. 5′-Ends of the DNA strands are represented by dots, 3′-ends are represented by arrows, and DNA synthesis is indicated by dashed lines.